1. Field of the Invention
The present invention relates to cleaning solution for removing a residue after an ashing process in a manufacturing process for a semiconductor device, and a manufacturing method for a semiconductor device using the cleaning solution, and, more particularly, to cleaning solution to be used in manufacturing a semiconductor device provided with a nickel silicide layer, and a manufacturing method for the semiconductor device.
2. Description of the Related Art
With the recent miniaturization and enhancement of the performance of system LSIs (Large Scale Integrated circuits), there is a demand for lowering the resistances of a diffusion layer (a source region and a drain region) for forming a transistor. Studies have been made on a scheme of forming a silicide layer to be formed on the diffusion layer using a nickel silicide having a lower resistance than a cobalt silicide, which has been used conventionally in order to decrease the contact resistance of the source region and the drain region
When holes and wiring grooves or the like are formed in the manufacturing process for a semiconductor device, in general, a resist pattern is formed using the lithography technology, dry etching is performed using the resist pattern as a mask, then an ashing process to ash the resist pattern with a plasma or the like is executed, and residues sticking on the wafer surface and inside of holes are removed with cleaning solution. As the residues remaining after the ashing process, ashing residues, such as incompletely ashed product and oxide of the resist produced by the ashing process adheres on the wafer surface, and etching deposition produced at the time of dry etching adheres inside the holes.
Conventional cleaning solutions to remove those residues include RCA cleaning solution or the like which is comprised of acidic cleaning solution, such as sulfuric acid/hydrogen peroxide/water mixture (SPM), and alkaline cleaning solution, such as ammonium hydroxide/hydrogen peroxide/water mixture (APM). Other cleaning solutions include solution containing an amine compound, such as hydroxyl amine, a solution containing fluorine-containing compound, such as ammonium fluoride, a solution containing both amine compound and fluorine-containing compound, solution containing organic acid, and a solution containing both organic acid and fluorine-containing compound.
There are cleaning solutions proposed for a substrate on which a Cu wiring and a low-dielectric interlayer insulating film are formed (see, for example, Japanese Patent Application (JPA) No. 2003-167360, JPA No. 2003-280219, and JPA No. 2003-313594). The photoresist residue removing solution described in JPA No. 2003-167360 suppresses corrosion of the wiring material and degrading of the interlayer insulating film by using a composition containing one or more compounds selected from a group of aliphatic polycarboxylic acids and aliphatic polycarboxylate, and one or more compounds selected from a group of reducing compounds and salts thereof. The photoresist residue removing solution described in JPA No. 2003-280219 prevents corrosion of the wiring material and damages on a barrier metal layer and the interlayer insulating film by using a composition containing one or more fluorine-containing compounds and one or more compounds selected from a group of glyoxylic acid, ascorbic acid, glucose, fructose, lactose and mannose. Further, the cleaning solution described in JPA No. 2003-313594 contains fluoride ions having a concentration of 0.001 to 1 mass % and pH of 2 to 7, thereby preventing dissolution and deterioration of a low-resistance metal film and a low-dielectric interlayer insulating film.
The prior arts however have the following problems. While cobalt silicide is not dissolved in the RCA cleaning solution, nickel silicide is dissolved in the RCA cleaning solution. When a substrate on which nickel silicide layer is formed is cleaned with the RCA cleaning solution which has conventionally been used in cleaning a substrate on which cobalt silicide layer is formed, the deposit can be removed with a problem that the nickel silicide layer is dissolved. It is not desirable that the nickel silicide layer dissolves and becomes thinner, for the contact resistance increases. Dissolution of the nickel silicide layer by cleaning is more noticeable on the nickel silicide layer which is not doped with an impurity than on the nickel silicide layer doped with an impurity. Particularly, the dry-etched upper layer portion or the portion where a through hole is formed is likely to dissolve.
The cleaning solution containing amine compound and the cleaning solution containing organic acid as described in JPA No. 2003-167360 have a problem on the removability of ashing residue. The cleaning solution containing amine compound and fluorine-containing compound, the cleaning solution containing fluorine-containing compound as described in JPA No. 2003-313594, and the cleaning solution containing organic acid and fluorine-containing compound as described in JPA No. 2003-280219 have a problem such that the composition range and the concentration range capable of completely removing residues without damaging a nickel silicide layer are extremely narrow. For example, the cleaning solution containing amine compound and fluorine-containing compound, which may lead to a longer process time and is thus not fit for a cleaning method that demands fast processing, such as single wafer cleaning. The cleaning solution containing fluorine-containing compound and the cleaning solution containing organic acid and fluorine-containing compound cannot be used in processes that cause a density change, such as a process which recycles chemical solution, for the cleaning solutions suffer a narrow range for not damaging the nickel silicide layer.
While the cleaning solutions described in JPA No. 2003-167360, JPA No. 2003-280219 and JPA No. 2003-313594 are said not to damage wiring material and an interlayer insulating film, the wiring material and the interlayer insulating film, if dissolved, do not matter at all for they are 300 nm thick or thicker. As the nickel silicide layer is very thin, about 10 nm thick, and is expected to become thinner in the future, even a slight change in thickness may greatly influence the contact resistance and may cause an operational failure.